Refactor Token Identification

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What does this MR do and why?

This MR refactors the Token Identification of the AgnosticTokenRevocationService and the Token Information API. We reduce code duplication by having the identification handled in a single place.

Issue: #499247 (closed)

🛠 with ❤ at Siemens

MR acceptance checklist

MR Checklist ( @nwittstruck)

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the javascript style guides
• Conforms to the database guides

How to set up and validate locally

See !165157 (merged) and !153376 (merged)

Related to #499247 (closed)